Blowback??

[Ciner]

Guys can you explain to me exactly what blowback is and what problems it causes? Also how do you fix it?

[Tom]

http://www.fatbobsdirect.com/forum/showthread.php?s=&threadid=1695

To fix this, you need to increase the amount of time the bolt stays forward after firing (usually called the 'dwell' time).

[Parksy]

Also depends what the marker is as to how to fix it.

Another cause of blowback can be paint being too tight in the barrel...

[Tom]

Originally posted by L1f3
Another cause of blowback can be paint being too tight in the barrel...

That shouldn't cause blowback - if it does then it means your bolt isn't properly sealing the breech. Having said that, most bolts don't properly fit the breech, let alone properly seal it :)

[Parksy]

If a ball is too tight in the barrel it means that excess air has no where to travel, other than back out of the breech into the feed tube causing blowback :) Had it on my Evo cocker with a batch of big paint :)

Best way on a cocker to test for it is to drop a few balls in the feed (no hopper attached to marker) and fire one off, the second ball should really just drop into the breech. If the ball jumps up you have blowback...

[Ciner]

Cheers!
The gun is a JT 6.0! Does anyone know how to sort the problem?

[Tom]

Buy a new marker :D

[Parksy]

Originally posted by Tom
Buy a new marker :D

I concur :p

[sheggy]

Most often in your type of gun (open bolt blowback) the problem is there is not enough gas being released by the valve to either get the desired velocity or re-cock the bolt, easiest way to overcome that is to change or alter the spring in the valve so it allows enough gas to ballance things out, it's a bit of a trial and error way, might be a good idea to get a spring kit.

[Tom]

What? So you are saying that blowback is caused by not enough gas through the marker? While what you described can be a common problem in such markers, I don't think it's got anything to do with this, especially when the guy specifically said right at the start that the problem was blowback.

[Tom]

Originally posted by L1f3
If a ball is too tight in the barrel it means that excess air has no where to travel, other than back out of the breech into the feed tube causing blowback :) Had it on my Evo cocker with a batch of big paint :)

Sorry - I wasn't disagreeing with you - I just said that it *shouldn't* cause blowback - because the bold *should* properly seal the breech. Sadly, most don't...

[sheggy]

Blowback is just the amount of gas needed to recock and attain good velocity becoming off ballance in a blowback marker, low pressure markers are another story.

[Tom]

In this context, blowback is http://fatbobsdirect.com/forum/showthread.php?s=&threadid=1695 definition (2).

[Fatbobs]

If the problem is gas blowing back through the gun and into the hopper then this is caused by a worn "O" ring in the bolt (the one behind the hole)

Andy